The present invention relates to computer disk drives, and more particularly, to a disk clamp for a disk drive, and an apparatus and method for preloading the disk clamp in order for installation within the disk drive.
Disk drive data storage systems typically include one or more data storage disks mounted to a spindle hub, and a spindle motor drives the spindle hub which rotates the disks at high RPMs. A disk clamp assembly secures the disks to the hub.
Data disks have a central bore or opening that receives the spindle hub. A common type of disk clamp assembly includes an annular or disk-shaped disk clamp, and a number of screws that secure the clamp to the hub. One or more disks positioned below the clamp are secured to the hub. In addition, spacers may be placed between each disk. For example, in a disk drive with a single data disk, the arrangement could include in series, a clamp, a spacer adjacent the clamp, a disk, a spacer on the opposite side of the disk, and then the hub. For some disk clamp assemblies, a top data disk may directly contact the disk clamp without the use of a spacer. The disks and spacers are often referred to as a disk pack.
Examples of references disclosing clamps utilizing securing screws include the U.S. Pat. Nos. 5,274,517, 5,333,080, 5,528,434, and 5,790,345.
Certain disadvantages arise by using screws to secure the clamp to the hub. One distinct disadvantage is that the screws transmit irregular radially and axially directed forces to the data disk, thus resulting in surface irregularities on the disk. Any distortion or surface irregularities of the disk read/write surface may result in poor head transducer flight characteristics. Another disadvantage is that use of screws contributes to disk contamination. Particle generation occurs when the screws are driven for attaching the clamp. More specifically, particle generation can be attributed to screw-to-hole and screw-to-driver misalignments, excessive force transferred through a single screw, excessive friction for the screw to overcome when being driven, and other reasons as well. In order to rectify these problems, efforts can be made to redesign screw-to-driver interface, improve tool alignment for driving the screw, and even lubricating the screw. Each of these solutions may involve significant redesign of not only the screws and the tools used to drive the screw, but may also require disk clamp redesign. Furthermore, lubrication of the screws can cause contamination by introduction of a substance into the disk drive which itself is a contaminant, or which attracts contaminants.
Another type of disk clamp exists which does not require the use of screws to secure the clamp to the hub. Presumably, these types of clamps help to reduce undesirable radial or axial loading and also help to reduce contamination. One example of a clamping device which does not require the use of screws to secure a clamp to the hub includes the device disclosed in the U.S. Pat. No. 5,270,999. The disk clamp disclosed in this references has a flat lower surface which directly contacts the data disk. The central opening of the clamp includes an inner conical surface. The upper end of the hub includes a groove having a complementary conical or angled surface. When the clamp is mounted over the hub, a uniform circumferential gap exists between the conical surfaces. A clip or retaining ring is placed in the gap between the conical surfaces. When the retaining ring is in place, the clamp resists axial force that may act to disengage the disk from the hub. In addition to the clip or retaining ring, an O-ring is also used to stabilize the disk with respect to the hub. The clamp disclosed in the U.S. Pat. No. 5,270,999 provides very little axial force to secure the disk or disks to the hub. Thus, the O-ring must be used to help prevent radial movement of the disk with respect to the hub. There is always some small gap between the inner edge of the disk defining the central opening and the outer surface of the hub. This gap can allow radial movement of the disk with respect to the hub if no force is provided to prevent such radial movement.
The current method used for installing a screwless clamp involves the use of a press device which deflects the clamp after the clamp has been placed over the hub of the disk drive. Additionally, this method also involves placing a load on the retainer ring as the retainer ring is placed in the gap between the hub and the disk clamp. Therefore, in addition to the force which is needed to deflect the clamp, additional force is required to overcome the friction between the retainer ring and the edge of the interior or central opening of the disk clamp such that the retainer ring can slide or move into the gap between the hub and the clamp. Also in this method, because the disk clamp is loaded and mounted for use over the hub, structure is required to stabilize the hub to prevent damage to the hub. The data disks themselves must be prevented from spinning, and the current solution for this is to create holes in the housing or baseplate of the disk drive, and then spanners are placed in contact with the lower edge of the disk pack to prevent it from spinning. Thus, the current method of installing a disk clamp still subjects the disk drive to contamination and potential damage. Therefore, even in the case of a screwless clamp, there are certain problems which arise in installing the disk clamp.
Therefore, there is a need to provide an apparatus and method which allows for easy and reliable installation of a disk clamp, yet minimizes potential damage to the disk drive, and also simplifies the tools/equipment which must be used to install the disk clamp. Accordingly, there also is a need for a screwless disk clamp of the type which accommodates the apparatus and method for installing the disk clamp.
In accordance with the present invention, a disk clamp and an apparatus and method for preloading the disk clamp are provided. The invention may also be regarded as a combination of the disk clamp, along with the apparatus for preloading the disk clamp. The invention herein is also intended to cover various subcombinations of this combination, including various elements used within the preloading apparatus. Additionally the invention herein is also intended to cover methods of installing the disk clamp in the disk drive incorporating the method of preloading the disk clamp.
In a preferred embodiment of the disk clamp, the disk clamp includes a lower flange or proturbance which contacts an underlying spacer or disk. When an external load is applied to set the clamp, the disk clamp itself acts as a spring in that it deflects downward in response to the applied load. After a retaining ring is placed in a gap between a groove on the hub and the clamp, the load is removed which enables the disk clamp to spring back to its undeflected state; however, the retaining ring prevents full return resulting in the retaining ring being wedged between the clamp and the hub. A continuous wire ring retaining ring may be used, a cutring, or multiple sections of wire arcs may be inserted between the clamp and the hub.
Other structural features of the disk clamp include an upper groove formed in the upper surface of the clamp for receiving a balance ring, and one or more lower concentric grooves. These lower concentric grooves help to distribute the load of the clamp on the underlying disk pack. Specifically, the ability to vary and control the load transmitted from the disk clamp to the disk pack minimizes deflection known as disk coning and waviness. Preferably, the contact surface of the lower flange is flat, which further reduces undesirable radial loading thus reducing disk coning and waviness. The larger contact area provided by the flat contact surface of the lower flange better compensates for locational misalignment between the clamp and a disk pack which naturally occurs due to tolerances in the manufacture of the clamp and of the disks. Particle generation resulting from movement of the contact surface relative to the disk is minimized thereby reducing disk drive contamination. The flat contact surface of the clamp remains in its contact position against a disk/spacer even during thermal cycles. Thus, there is no movement or displacement between the clamp contacting surface and the underlying disk/spacer. A rounded disk contact surface may displace (e.g., curl/uncurl) in response to thermal cycles which contributes to undesirable particle generation caused by a movement of the contact surface across the underlying disk/spacer.
The disk clamp of the present invention eliminates the need for using screws to secure the clamp to the hub. The clamp provides an axial force upon the disk pack which prevents the disk(s) from both axial and radial displacement with respect to the hub. O-rings or other stabilizing elements are not required to stabilize the connection between the disk pack and the hub because of the axial force which is provided by the disk clamp.
The method of preloading the disk clamp according to the present invention contemplates the use of a preloading device which secures the disk clamp, and deflects the disk clamp a desired amount allowing the disk clamp to be positioned over the hub of the disk drive for installation of the disk clamp. The method of preloading the disk clamp can also be included within a method of installing the disk clamp in the disk drive. Accordingly, the invention herein not only includes the method of preloading the disk clamp, but also includes a method for disk clamp installation on the disk drive. The method of installing the disk clamp can be incorporated either within displacement or movement of the disk drive assembly to the preloaded disk clamp, or movement/displacement of the preloaded disk clamp to a stationary disk drive.
The preloading device of the invention is disclosed in reference to three preferred embodiments. Common to each of these embodiments is application of an axial force which deflects the disk clamp and maintains the disk clamp in its deflected state. The preloading device also includes a component for emplacing the retainer ring after the deflection of the clamp. The preloading device may be manually operated, or may be incorporated within an automated assembly or rework process. In a first embodiment of the preloading device, the disk clamp is secured within the preloading device, and means are provided for applying a load to deflect the disk clamp. The means for loading may include a handle which provides the desired mechanical advantage in application of the load to the clamp. The preloading device may then be moved to the location of the disk drive for installation of the disk clamp. A separate component is used to emplace the retainer ring. This component is inserted into an opening within the preloading device, and is then operated to force the retainer ring between the hub of the drive and the clamp.
In a second embodiment of the preloading device, means are provided for applying load to the disk clamp in the form of an overhead press assembly which may be incorporated within an automated assembly process. Integrated within this press assembly are components for emplacing the retainer ring as well. In this embodiment, it is contemplated that the disk clamp remain stationary within the preloading device, and then the disk drive assembly is moved to the preloaded disk clamp for installation of the disk clamp.
In a third embodiment of the preloading device, means are provided for applying a load to the clamp by use of a screw type press which can be either manually or automatically operated. As with the first and second embodiments, the third embodiment also includes a component for emplacing the retainer ring to complete installation of the disk clamp within the disk drive.
The disk clamp of the present invention, along with the methods of preloading and installation, and the various preloading devices each have a number of advantages. Use of a screwless disk clamp simplifies the overall disk clamp and hub arrangement, thus minimizing the cost of fabrication and assembly, reducing the likelihood of malfunction in the disk drive system, and providing effective and consistent disk drive performance. A preloading device which is able to preload the disk clamp further reduces potential disk drive contamination and damage. The preloading device further simplifies the construction of the disk drive because there is no need to provide additional support to the hub during clamp installation, and no separate means are required to prevent the disk pack from spinning during the installation.
Other advantages of the invention will become apparent from a review of the, following detailed description, taken in conjunction with the accompanying drawings.